This invention concerns a continuous ballast-tamping machine with independent tamping heads for railway lines.
To be more exact, the invention concerns a ballast-tamping machine able to run with a uniform motion on a railway line to be tamped; the tamping unit of the machine is provided with horizontal alternating motion and comprises tamping tine-holder heads capable of vertical movement independently of each other.
Such heads impart a vertical alternating motion to the tine-holders, and to the tamping times connected thereto, independently of each other on each quadrant of the rail/sleeper attachment.
The machine obtains thereby a much lighter general structure and great working flexibility with regard to equipment included in the railway line, such as switches and crossings, and various obstacles, such as double sleepers and the like.
The state of the art covers ballast-tamping machines which work on railway lines with various operating methods.
Some machines work discontinuously and halt at each sleeper or group of sleepers where tamping is to be performed.
Other machines work continuously; the tamping units on them are halted momentarily in correspondence with the sleepers while the machine continues its movement along the line.
The machines which work continuously are more productive and provide different concepts regarding the embodiment of the units performing the tamping work but are more complex and, above all, have greater dimensions and heavier weights than the machines which work discontinuously.
There are also continuous machines in which the main motive vehicle incorporates a bogie, or satellite vehicle, that bears the tamping units, the bogie being equipped with its own means for running on the railway line.
The bogie moves with an alternating motion in relation to the main vehicle and comprises bodies of a great size, this being required to impart to the tamping units the necessary force and energy for penetration into the ballast.
These great bodies have an unfavourable effect on the evenness of the movement of the motive vehicle when the latter has to transmit motion mechanically to the satellite vehicle.
Continuous machines have also been designed which comprise tamping units that are closely anchored in a vertical direction to the structure of the motive vehicle and can run horizontally on that vehicle.
Such machines entail generally a lighter overall structure than the types having a satellite vehicle and comprise parts cooperating with much smaller bodies engaged in a horizontal alternating motion.
Such smaller bodies enable the ballast-tamping machine to work more evenly, but there are still grave structural problems regarding absorption of the tamping stresses.
A machine of this type is disclosed, for instance, in DE 1067837.
GB 2,148,361 discloses tamping heads which can move vertically and are contained in one single body, that is to say, they are not independent of each other as regards positioning or adjustment. The one single independent movement of the tools is obtained to avoid contact with the rails when there are double lines or switches.
US 4,369,712 discloses tamping means in one single body of several tamping heads with tine-holders fixed to the body, the body being adjustable as one overall whole and not as regards the individual heads. The independent action of the individual groups of heads is obtained by groups on the same side of the line.
The continuous machines of the state of the art have very complex and heavy tamping structures that bear and move the tines working on the ballast since the vertical alternating motion is imparted to the whole operating unit including the structure, the vibration system and the system for extending and retracting the tine-holders.
Such tamping structures, whether they are provided with a pendular, oscillatory motion or a horizontal, alternating motion, are moved, in any event, vertically together with the tine-holders and tines during the path of approach and insertion of the tines into the ballast.
This entails the vertical movement of heavy bodies and unfavourable structural repercussions from a structural and functional viewpoint.
Moreover, when they coincide with the equipment of the railway line, such as switches and crossings, or various obstacles, such as double sleepers and the like, these tamping structures may include complex systems for the temporary withdrawal of some of the tines from their working position, the tines being caused to rotate about a horizontal axis, for instance.
Cases may sometimes occur when the tamping work on the railway line is completely stopped.